Scalable modulator for frequency shift keying in free space optical communications

Area of Science:

• Optical communication
• Digital modulation techniques

Background:

• Frequency Shift Keyed (FSK) modulation is advantageous for high-loss communication links like those in deep space.
• FSK utilizes bandwidth expansion to compensate for power losses, similar to Pulse Position Modulation (PPM).
• Unlike PPM, FSK's bandwidth expansion does not necessitate wider bandwidths in electronic components.

Purpose of the Study:

• To present a novel Frequency Shift Keyed (FSK) modulator design.
• To evaluate the performance of the FSK modulator with varying bandwidth expansion.
• To assess the FSK transmitter's compatibility with different receiver types.

Main Methods:

• Developed an FSK modulator with a component count that scales logarithmically with bandwidth expansion.
• Tested the modulator at 5 and 20 Gbit/s with four-fold bandwidth expansion.
• Evaluated system performance using a pre-amplified receiver and a photon counting receiver.

Main Results:

• The FSK modulator demonstrated high performance, requiring only 4-5 dB above the theoretical best power with a pre-amplified receiver.
• The modulator was successfully tested at high data rates (5 and 20 Gbit/s).
• The FSK transmitter was also tested in conjunction with a photon counting receiver.

Conclusions:

• The developed FSK modulator is a viable technology for deep space and high-loss optical communication links.
• The modulator's design offers an efficient way to increase bandwidth expansion without proportional increases in electronic component complexity.
• The system shows promising results for future optical communication applications requiring robust power-loss compensation.